Electrical terminal

ABSTRACT

Disclosed is an electrical terminal whose principal use is in connecting a lead to a terminal area on a printed circuit board. The terminal is formed so that substantially all of the contact area on the terminal is brought into engagement with the terminal area on the printed circuit board. The terminal is also designed so that a spring pressure is applied at both the front and the rear of the terminal&#39;&#39;s contact area so that this area is constantly biased against the circuit board&#39;&#39;s terminal area thereby assuring an electrical junction between the two areas capable of carrying a substantial current load.

United States Patent [191 Cairns et a].

[ ELECTRICAL TERMINAL [75] Inventors: Thomas M. Cairns, Detroit; Robertv I). Kennedy, Northville, both of Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[22] Filed: Feb. 24, 1972 [21] App]. No.: 228,878

[52] US. Cl 339/252 R FOREIGN PATENTS OR APPLICATIONS 1,956,183 9/1970Germany 339/252 R [4 1 June 26, 1973 Primary ExaminerJoseph H. McGlynnAtt0rney-Keith L. Zerschling et al.

[5 7] ABSTRACT Disclosed is an electrical terminal whose principal useis in connecting a lead to a terminal area on a printed circuit board.The terminal is formed so that substantially all of the contact area onthe terminal is brought into engagement with the terminal area on theprinted circuit board. The terminal is also designed so that a springpressure is applied at both the front and the rear of the terminalscontact area so that this area is constantly biased against the circuitboards terminal area thereby assuring an electrical junction between thetwo areas capable of carrying a substantial current load.

12 Claims, 6 Drawing Figures PAIENTEDJHN25 1915 m m z i E- M ELECTRICALTERMINAL BACKGROUND OF THE INVENTION Many electricalterminals are knownfor connecting a lead to a terminal area on a printed circuit board.With knowledge of the many electrical terminals already available in theprior art for the stated purpose, the terminal of this invention wasdesigned by approaching its construction while considering all of themany aspects of terminal construction. In designing the terminal of thisinvention, such things as manufacturing feasibility, rapid output .onautomatic manufacturing machinery, ease of use by assembly personnel andself protecting features for the terminal were taken into considerationfrom the very outset of the terminals design. The terminal of thisinvention is designed so that it takes into account not only electricalcharacteristics required of the terminal but also manufacturingfeasibility as well.

The terminal of this invention is one which is so constructed that ithas many advantageous electrical characteristics. The terminal has acontact surface area that will lay in flat contact with an engagedterminal area of a printed circuit board. Also, the terminal is designedso that a spring pressure will be applied between the terminals contactarea and the boards terminal area during their engagement. The terminalis designed so that parallel circuit paths are provided between the leadattached to the terminal and the board's terminal area thus permitting alarger amount of current to be carried by the terminal. From amechanical standpoint, the terminal is designed so that an overstressingof the contact element thereof will not be permitted. Also, the terminalis designed to withstand rough handling and it has protective surfacesformed as an integral portion thereof to protect the spring members ofthe terminal from mishandling. For manufacturing feasibility, theterminal is designed so that large numbers of high quality terminals canbe produced rapidly ina progressive stamping operation.

SUMMARY OF THE INVENTION This invention relates to an electricalterminal and, more particularly, to an electrical terminal whichconnects a lead to a terminal area of a printed circuit board.

In accordance with the teachings of this invention, an electricalterminal is formed from a single, metal strip. The terminal has a bottomwall which has a front, a back and a pair of side edges. A pair of wallforming elements having side and top wall portions are also provided.The side wall portions of each of the elements extend upwardly from anopposed side edge of the bottom wall and each of the top wall portionsof the elements extendinwardly from an opposed edge of an associated oneof the side wall portions to form at least half of the entire top wallof the terminal. Each of the top wall portions of the wall formingelements are notched to define an opening in the top wall. A surface ofthe top wall adjacent the front of the terminal forms an initial topwall surface. A terminal element extends from the front edge of thebottom wall of the terminal and this element has, in order, a firstspring member having a radius surface portion and a lead radius portion,a weakened section, a contact surface, a second spring member, and afoot. The radius surface portion of the first spring member of theterminal element extends from the front edge of the bottom wall andcurves upwardly and inwardly of the bottom wall to a point engaging therear edge of the initial top wall surface to store an amount of stressin the terminal element. The lead radius portion of the first springmember extends upwardly from the radius surface portion through andbeyond the top wall to a point which is tangent to a horizontal plane,which plane is parallel to the terminals bottom wall but spaced aboveits top wall. The weak ened section interconnects at the tangent point,the

first spring member and the contact surface. The contact surface, whichconnects with the terminal area of the printed circuit board, is at aslight downward angle to the mentioned horizontal plane. The secondspring member .of the terminal element extends downwardly from the rearof the contact surface through the opening of the terminals top wallinto the interior of the ter minal. The foot terminates the secondspring member and the foot contacts the bottom wall of the terminal. Agripper device extends from the back edge of the terminals bottom wallto secure a lead to the terminal.

In greater detail, the top wall portions of the pair of wall formingelements are notched to define at least a front and a rear opening inthe terminals top wall with an intervening surface therebetween. Thelead radius portion of the first spring member extends out of the frontopening and the second spring member extends into the second opening.The intervening surface has an upwardly facing projection formed thereonfor engaging the contact surface whenthat surface is pushed downwardlyfrom a normal position more than a desired amount thereby to preventoverstressing of the terminal element. The height of the projectionabove the intervening surface controls the degree to which the terminalelement may be stressed.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT In the drawings, the electrical terminal of this invention isgenerally designated by the numeral 10. The terminal has a bottom wall12 which is in the form of a rectangle having a pair of side edges, afront edge and a back edge. The electrical terminal is formed from aunitary piece of conductive metal. A pair of wall forming elements,generally designated by the numerals 14 and 16, each have side, top, andfront wall portions. In the case of the wall forming element 14, theside wall portion thereof is 18, the top wall portion thereof is 20, andthe front wall portion thereof is 22. In the case of the wall formingelement 16, the side wall portion thereof is 24, the top wallportionthereof is 26, and the front wall portion thereof is 28. Each of theside wall portions 18 and 24 extends upwardly from an opposed side edgeof the bottom wall 12. Each of the top wall portions 20 and 26 extendinwardly from an opposed edge of an associated one of the side wallportions to form at least half of the entire top wall of the terminal(best seen in FIG. 1).

The top wall portion 20 is notched to provide openings 30 and 32 thereinas is best seen in FIGS. 1 and 4. Similarly, the top wall portion 26 isnotched to provide openings 34 and 36 therein. The openings 30 and 34combine to provide a front opening for the top wall of the terminalwhile the openings 32 and 36 combine to form a rear opening for the topwall of the terminal.

Projecting portions 38, 40 and 42 are formed on the top wall portion 20as best seen in FIGS. 1 and 4. Similarly, projecting portions 44, 46 and48 are formed on the top wall portion 26. The projecting portions 38 and44 combine to form an initial top wall surface. The projecting portions40 and 46 combine to form an intervening surface between the openings ofthe top wall. The projecting portions 42 and 48 combine to form a reartop wall for the terminal.

Each of the front wall portions 22 and 28, respectively of the wallforming elements 14 and.16, extend outwardly from the projectingportions 38 and 44. The front wall portions 22 and 28 are curveddownwardly and together they provide a guiding surface which aids indirecting the terminal into an opening of a connector block (not shown).The guiding surface also functions to protect the active terminalelement of the terminal 10 from damage during terminal insertion. Theprojecting portion 46 of the top wall portion 26 of the wall formingelement 16 has an upstanding projection 50 formed thereon for purposesto be described hereinafter.

A terminal element, generally indicated by the numeral 52, is providedas a principal element of the terminal 10 of this invention. Theterminal element 52 is divided into the following principal parts: afirst spring member, generally identified by the numeral 53 whichincludes a radius surface portion 54 and a lead radius portion 56, aweakened section 58, a contact surface 60, a second spring member 62,and a foot 64.

The radius surface portion 54 of the first spring member 53 of theterminal element 52 extends upwardly and inwardly of the bottom wall 12of the terminal 10. This surface 54 engages the rear edge of the initialtop wall surface defined by the projecting portions 38 and 44 of the topwall portions and 26 respectively of the wall forming elements 14 and16. The engagement of the radius surface portion 54 with this surfaceserves to pre-stress and store that stress in the terminal element 52.

The lead radius portion 56 of the first spring member 53 extends fromthe radius surface portion 54 outwardly through the front openingprovided in the top surface of the terminal 10. This first spring member53 serves to provide a spring force on the contact surface 60 when thecontact surface is in engagement with a terminal area of a printedcircuit board. As is best understood by reference to FIG. 2, the member53 extends upwardly to a point 66 which is tangent to an imaginary plane68. The plane 68 is parallel to the bottom wall 12 but spaced upwardlyand above the top wall of the terminal.

At the tangent point 66, the weakened section 58, which is weakened byproviding a rectangular shaped depression in the underpart of theterminal element 52 at this point, is employed to interconnect thecontact surface 60 with the first spring member 53. Placement of theweakened section 58 at this tangent point 66 is critical in that suchplacement insures that the first spring member 53 and the second springmember 62 will act on the contact surface 60 to force the contactsurface into intimate contact with a terminal area of a printed circuitboard and provide a flat, uniform junction therebetween. The weakenedsection, in effect, acts to direct the point of bending of the contactarea into engagement with a terminal area of a printed circuit boardwhen the same is deformed thereagainst. When such a contact is made in aflat manner, a parallel circuit path is obtained through the terminal10. One path is through the first spring member 53 and the contactsurface 60 while the other path is through the second spring member 62and the contact surface.

The contact surface 60 of the terminal element 52, in a normal conditionas shown in the drawings, is at a slight downward angle with respect tothe imaginary plane 68. The preferred downward angle is about 3. Thedownward angle is selected so that the contact area will properlyflatten against the contact area of the printed circuit board when it isbrought into contact therewith. The flattening of the contact surfacecomes about because the contact surface 60 is depressed downwardlytoward the upstanding projection 50. This downward depression isresisted by the first spring member 53 on one side of the contactsurface and by the second spring member 62 and on the other side of thecontact surface. The position of the contact surface 60 with respect tothe first spring member 53 may change slightly at the weakened section58 so that the contact surface 60 is deformed into a complete areacontact with the terminal area of the printed circuit board. After sucha contact has been established, the spring members 53 and 62 serve toapply a continuous spring force on opposite ends of the contact area toassure that this contact area is held in flat, parallel engagement withthe printed board terminal area.

The second spring member 62 of the terminal element 52 extendsdownwardly from its point of engagement with the contact surface 60through the rear opening in the top wall of the terminal 10. As is bestunderstood by reference to FIGS. 1 and 4, the second spring member 62tapers inwardly as it progresses downwardly to its terminal point. Thereason that the member is tapered is so that it will gve a greaterspringback than a simple linear member. This is an optimization of thespring member deflection characteristic.

The foot 64 of the terminal element 52 terminats the second springmember 62. The foot 64 is in engagement with the bottom wall 12 of theterminal 10. The foot has an upturned shape so as to guarantee that thesecond spring member 62 will not dig into the botton wall. The foot 64allows the second spring member 62 to slide across the bottom surface sothat the contact surface 60 may be displaced downwardly as viewed inFIGS. 2 and 5.

An opening is provided in the bottom wall of the terminal 10 as bestseen in FIGS. 2 and 5. The purpose of this opening 70 is to provide aspace into which a locking finger may be moved to lock the, terminal 10within a connector block (not shown). The locking finger arrangement maybe similar to that described in U.S. Pat. No. 3,601,760 issued on Aug.24, 1971 to T.

M. Cairns.

The upstanding projection 50 is formed on the projecting portion 46 ofthe top wall portion 26 of the wall forming element 16 is designed sothat the contact portion 60 of the terminal element 52 will not beoverstressed because the terminal element can not be deformed beyond apredetermined limit. In particular, the contact surface 60 may bedeformed downwardly from the plane 68 only to the point at which thebottom of the contact surface engages the upstanding projection 50. Thislimits the total travel of the contact surface and the limit is sodesigned that the terminal element 52 is not unacceptablyoverstressedfUpon release of the deforming pressure, the terminalelement 52 will substantially return to its normal position.

To the rear of the bottom wall 12 is formed a gripper structuregenerally designated by the numeral 72. This gripper structure isdesigned to engage and hold the bare ends of an electrical lead wire(not shown) therewithin. Such a structure, is well known in the art andno further description will be included herein.

There has been disclosed herein a preferred embodiment of an electricalterminal in accordance with the teachings of this invention. Manymodificationsof this disclosed electrical terminal will be apparent tothose skilled in the art in view of the detailed teachings of thisspecification. It is intended that all such modifications which fallwithin the true spirit and scope of this invention be included withinthe scope of the appended claims.

We claim:

1. An electrical terminal formed from a single metal strip whichcomprises:

a bottom wall having front, back and side edges;

a pair of wall forming elements having side and top wall portions; eachof said side wall portions extending upwardly from an opposed side edgeof said bottom wall; each of said top wall portions extending inwardlyfrom an opposed edge of an associated one of said side wall portions toform at least half of the entire top wall of the terminal, each of saidtop wall portions being notched to define an opening over at least aportion of said top wall, each of said top wall portions forming aninitial top wall surface adjacent the front of the terminal;

, a terminal element extending from said front edge of said bottom wall,said terminal element having, in order, a first spring member having aradius surface portion and a lead radius portion, a weakened section, acontact surface, a second spring member, and a foot; said radius surfaceportion of said first spring member curving upwardly and inwardly ofsaid front edge of said bottom wall to a point engaging the rear edge ofsaid initial top wall surface defined by said top'wall portions therebyto store an amount of stress in said terminal element; said lead radiusportion of said first spring member extending upwardly from said radiussurface portion through and beyond said opening in said top wall to apoint tangent to a horizontal plane, which plane is parallel to saidbottom wall but spaced above said top wall; said weakened section atsaid her extending downwardly through said opening of said top wall intothe interior of said terminal; said foot terminating said second springmember and contacting said bottom wall; and

gripper means extending from said back edge of said bottom wall forsecuring a lead to the terminal.

2. The electrical terminal as defined in claim 1 wherein: said top wallportions of said pair of wall forming elements are notched to define atleast a front opening and a rear opening in said top wall with anintervening surface therebetween; said lead radius portion of said firstspring member extending out of said front opening and said second springmember extending into said second opening; said intervening surfaceproviding a stop surface which is engaged by the underside of saidcontact surface to prevent overstressing of said terminal element.

3. The electrical terminal as defined in claim 2 wherein: an upwardlyfacing projection is formed on said intervening surface, said projectionengaging the underside of said contact surface when said surface isdeformed a determined amount to prevent overstressing of said terminalelement, the height of said projection above said intervening surfacecontrolling the degree to which said terminal element may be stressed.

4. The electrical terminal as defined in claim 1 wherein: said slightdownward angle of said contact surface with respect to said horizontalplane is no more than 3.

5. The electrical terminal as defined in claim 1 further including:front wall portions formed on said pair of wall forming elements, eachof said front wall portions extending forwardly from an associated oneof said top wall portions defining said'initial top wall surface, saidfront wall portions forming a guiding surface for terminal insertion.

6. The electrical terminal as defined in claim 1 wherein: said weakenedsection is formed by deforming a portion of the metal of said terminalelement to a thickness less than the thickness of said metal.

7. The electrical terminal as defined in claim 1 wherein: saidsecond'spring member tapers inwardly from said contact surface to saidfoot.

8. An electrical terminal formed from a single, metal strip whichcomprises:

a bottom wall having front, back and side edges;

a pair of wall forming elements having side, top and front wallportions, each of said side wall portions extending upwardly from anopposed side edge of said bottom wall; each of said top wall portionsextending inwardly from an opposed edge of an associated one of saidside side wall portions to form at least half of the entire top wall ofthe terminal, each of said top wall portions having notches thereinproviding openings in both the front and the rear of said entire topwall, the surfaces of said top wall portions forming both an interveningsurface between said openings and an initial top wall surface adjacentthe front of the terminal; each of said front wall portions extendingforwardly and downwardly from a respective one'of said top wall portionswhich forms said initial said top wall surface to provide a terminalnose surface; a terminal element extending from said front edge of saidbottom wall, said terminal element having, in order, a first springmember with a radius surface portion and a lead radius portion, aweakened section, a contact surface, a second spring member, and a foot;said radius surface portion of said first spring member curving upwardlyand inwardly of said front edge of said bottom wall to a point engagingthe rear edge of said initial top wall surface; said lead radius portionof first spring member extending upwardly from said radius surfaceportion through and beyond said front opening in said top wall to apoint tangent to a horizontal plane, which plane is parallel to saidbottom wall but spaced above said top wall; said weakened section atsaid tangent point interconnecting said first spring member and saidcontact surface; said contact surface being at a slight downward anglewith respect to said horizontal plane, said contact surface overlying but spaced above said intervening surface of i said top wall; said secondspring member extending downwardly from said contact surface throughsaid rear opening of said top wall into the interior of the terminal;said foot terminating said second spring member and contacting saidbottom wall; and gripper means extending from said back edge of saidbottom wall for securing a lead to the terminal.

9. The electrical terminal as defined in claim 8 wherein: an upwardlyfacing projection is formed on said intervening surface, said projectionengaging the underside of said contact surface when said surface isdeformed a determined amount to prevent overstressing of said terminalelement, the height of said projection above said intervening surfacecontrolling the degree to which said terminal element may be stressed.

10. The electrical terminal as defined in claim 8 wherein: said slightdownward angle of said contact surface with respect to said horizontalplane is no more than 3.

11. The electrical terminal as defined in claim 8 wherein: said weakenedsection is formed by deforming a portion of the metal of said terminalelement to a thickness less than the thickness of said metal strip.

12. The electrical terminal as defined in claim 8 wherein: said secondspring member tapers inwardly from said contact surface to said foot.

1. An electrical terminal formed from a single metal strip whichcomprises: a bottom wall having front, back and side edges; a pair ofwall forming elements having side and top wall portions; each of saidside wall portions extending upwardly from an opposed side edge of saidbottom wall; each of said top wall portions extending inwardly from anopposed edge of an associated one of said side wall portions to form atleast half of the entire top wall of the terminal, each of said top wallportions being notched to define an opening over at least a portion ofsaid top wall, each of said top wall portions forming an initial topwall surface adjacent the front of the terminal; a terminal elementextending from said front edge of said bottom wall, said terminalelement having, in order, a first spring member having a radius surfaceportion and a lead radius portion, a weakened section, a contactsurface, a second spring member, and a foot; said radius surface portionof said first spring member curving upwardly and inwardly of said frontedge of said bottom wall to a point engaging the rear edge of saidinitial top wall surface defined by said top wall portions thereby tostore an amount of stress in said terminal element; said lead radiusportion of said first spring member extending upwardly from said radiussurface portion through and beyond said opening in said top wall to apoint tangent to a horizontal plane, which plane is parallel to saidbottom wall but spaced above said top wall; said weakened section atsaid tangent point interconnecting said first spring member and saidcontact surface; said contact surface being at a slight downward anglewith respect to said horizontal plane; said second spring memberextending downwardly through said opening of said top wall into theinterior of said terminal; said foot terminating said second springmember and contacting said bottom wall; and gripper means extending fromsaid back edge of said bottom wall for securing a lead to the terminal.2. The electrical terminal as defined in claim 1 wherein: said top wallportions of said pair of wall forming elements are notched to define atleast a front opening and a rear opening in said top wall with anintervening surface therebetween; said lead radius portion of said firstspring member extending out of said front opening and said second springmember extending into said second opening; said intervening surfaceproviding a stop surface which is engaged by the underside of saidcontact surface to prevent overstressing of said terminal element. 3.The electrical terminal as defined in claim 2 wherein: an upwardlyfacing projection is formed on said intervening surface, said projectionengaging the underside of said contact surface when said surface isdeformed a determined amount to prevent overstressing of said terminalelement, the height of said projection above said intervening surfacecontrolling the degree to which said terminal element may be stressed.4. The electrical terminal as defined in claim 1 wherein: said slightdownward angle of said contact surface with respect to said horizontalplane is no more than 3*.
 5. The electrical terminal as defined in claim1 further including: front wall portions formed on said pair of wallforming elements, each of said front wall portions extending forwardlyfrom an associated one of said top wall portions defining said initialtop wall surface, said front wall portions forming a guiding surface forterminal insertion.
 6. The electrical terminal as defined in claim 1wherein: said weakened section is formed by deforming a portion of themetal of said terminal element to a thickness less than the thickness ofsaid metal.
 7. The electrical terminal as defined in claim 1 wherein:said second spring member tapers inwardly from said contact surface tosaid foot.
 8. An electrical terminal formed from a single, metal stripwhich comprises: a bottom wall having front, back and side edges; a pairof wall forming elements having side, top and front wall portions, eachof said side wall portions extending upwardly from an opposed side edgeof said bottom wall; each of said top wall portions extending inwardlyfrom an opposed edge of an associated one of said side side wallportions to form at least half of the entire top wall of the terminal,each of said top wall portions having notches therein providing openingsin both the front and the rear of said entire top wall, the surfaces ofsaid top wall portions forming both an intervening surface between saidopenings and an initial top wall surface adjacent the front of theterminal; each of said front wall portions extending forwardly anddownwardly from a respective one of said top wall portions which formssaid initial said top wall surface to provide a terminal nose surface; aterminal element extending from said front edge of said bottom wall,said terminal element having, in order, a first spring member with aradius surface portion and a lead radius portion, a weakened section, acontact surface, a second spring member, and a foot; said radius surfaceportion of said first spring member curving upwardly and inwardly ofsaid front edge of said bottom wall to a point engaging the rear edge ofsaid initial top wall surface; said lead radius portion of first springmember extending upwardly from said radius surface portion through andbeyond said front opening in said top wall to a point tangent to ahorizontal plane, which plane is parallel to said bottom wall but spacedabove said top wall; said weakened section at said tangent pointinterconnecting said first spring member and said contact surface; saidcontact surface being at a slight downward angle with respect to saidhorizontal plane, said contact surface overlying bu t spaced above saidintervening surface of said top wall; said second spring memberextending downwardly from said contact surface through said rear openingof said top wall into the interior of the terminal; said footterminating said second spring member and contacting said bottom wall;and gripper means extending from said back edge of said bottom wall forsecuring a lead to the terminal.
 9. The electrical terminal as definedin claim 8 wherein: an upwardly facing projection is formed on saidintervening surface, said projection engaging the underside of saidcontact surface when said surface is deformed a determined amount toprevent overstressing of said terminal element, the height of saidprojection above said intervening surface controlling the degree towhich said terminal element may be stressed.
 10. The electrical terminalas defined in claim 8 wherein: said slight downward angle of saidcontact surface with respect to said horizontal plane is no more than3*.
 11. The electrical terminal as defined in claim 8 wherein: saidweakened section is formed by deforming a portion of the metal of saidterminal element to a thickness less than the thickness of said metalstrip.
 12. The electrical terminal as defined in claim 8 wherein: saidsecond spring member tapers inwardly from said contact surface to saidfoot.